Problem: Multiply.
Answer: Let's visualize to help us solve. There are $5$ groups of ${3}$. $3$ $+$ $3$ $+$ $3$ $+$ $3$ $+$ $3$ $+$ ${5} \times {3} = \underbrace{{3} + {3} + {3} + {3}+ {3}}_{{5}{\text{ threes}}} = 15}$ $15}={5}\times{3}$